This invention relates to a method and apparatus for degating molded parts using acoustic energy and, specifically, refers to a method and apparatus of degating or separating molded parts from a runner using high frequency sonic or ultrasonic energy. Quite specifically, molded thermoplastic parts are degated from a runner which is connected to the molded parts by individual gates using ultrasonic energy and an anvil, the top plate of which is dimensioned to undergo flexural motion of a substantially large motional amplitude at a frequency less than that of the applied sonic or ultrasonic frequency whereby to cause a burn out of the respective gates and freeing of the parts connected to the runner via the gates.
In molding thermoplastic parts, it is common practice to mold simultaneously a plurality of parts which are joined to a runner by means of individual gates. After the molding operation has been completed, the entire assembly comprising one or more runners and the plurality of attached parts is removed from the mold and the individual parts are separated from the runners. This process is known as degating. Degating is generally a manual operation which sometimes results in scarring of the molded part which scar may have to be smoothed off and removed using a mechanical abrading or polishing of the parts.
In addition, methods of degating molded parts from a runner include the use of acoustic energy. For example, in U.S. Pat. No. 3,595,453 entitled "Method of Separating Parts Using High Frequency Energy" an arrangement is shown in which molded parts attached to a runner are disposed upon a resilient support which in turn is disposed on a rigid base. When ultrasonic energy is applied to the runner the molded parts are degated from the runner.
A similar ultrasonic degating method is described in the book "Ultrasonics in Packaging and Plastics Fabrication" by Ralph H. Thomas, Sr., Cahners Books, Boston, Mass. (1974), pages 115-119.
In the prior art the molded parts and runner are placed upon a resilient support to ensure an out-of-phase relationship between the parts and the horn applying the ultrasonic energy.
Under certain conditions, such as when molded parts are to be degated as soon as they are removed from the molding machine while still hot, the degating process according to the prior art has met with varying degrees of success.
In order to improve the success of degating molded hot parts, in the present invention the resilient support and the rigid base are replaced by an anvil the top plate of which is dimensioned to undergo flexural motion of a substantially large amplitude at a frequency less than that of the applied sonic or ultrasonic frequency for causing the molded parts to undergo gross motion while the runner is subjected to sonic or ultrasonic energy for burning out of the respective gates coupling the parts to the runner.
A principal object of this invention, therefore, is the provision of a new and improved method and apparatus for separating a molded part from a runner or gate.
Another object of this invention is the provision of a new and improved method and apparatus for separating molded parts from a runner by the application of ultrasonic energy and use of an anvil the top plate of which is dimensioned to undergo flexural motion.
A further object of this invention is the provision of a new and improved method and apparatus for separating molded parts from a runner by the application of ultrasonic energy and use of an anvil the top plate of which is dimensioned to undergo flexural motion of a substantially large motional amplitude at a frequency less than that of the applied ultrasonic frequency to cause a burnout of the respective gates coupling the parts to the runner.
A still further object of this invention is the provision of a new and improved method and apparatus for degating molded parts from a runner by the application of ultrasonic energy and use of an anvil the top plate of which is dimensioned to undergo flexural motion of a substantially large motional amplitude at a frequency lower than that of the applied ultrasonic frequency to cause a burnout of the respective gates coupling the parts to the runner while the parts are still hot.
Further and still other objects of this invention will become more clearly apparent by reference to the following description when read in conjunction with the accompanying drawings.